Henrique, F. V., R. N. Parentoni, L. K. G. de Medeiros, A. W. de L. Brasil, K. D. S. de Oliveira, R. O. do Rego, A. P. de Souza, and P. I. da Nóbrega Neto. “Preoperative Epidural Administration of Morphine or Methadone for Analgesia in Female Dogs Undergoing to Ovariohysterectomy”. Brazilian Journal of Veterinary Medicine, vol. 39, no. 1, Mar. 2018, pp. 46-53, doi:10.29374/2527-2179.bjvm0253.